Mechanical classifier



Se ia. 30, 19% .s. A. ROTHELIUS 397779182 MECHANICAL CLASS IFIER Filed June 8, 1928 FOiAaAQ;

/AVENTUIQ seemed Sept. so, 1930 53.1 SI JO EL ROTHEJDIUS, 0F APPELVIKEN, STOQKHOLM', SWEDEN MEGHANICAL GLASSIFIER Application filed time 8, 1928. Serial No. 288,921.

The invention has for its object to improve the operation of classifiers of this type by preventing fine material from being removed with the coarse material.

To this end I add to the classifying action of the water which is based upon the fact that the heavier material settles, a more positive control by having the mechanical means for removing the coarse material to operate also as sieve members.

Another feature of my invention resides in the supply of additional washing water to the material on the sieves after they have left the liquid pulp in the settling portion of the tank.

Still other features of my invention will be apparent from the following detailed description and pointed out in the claim hereunto appended.

My invention is applicable to mechanical classifiers of all types, such as the Dorr, Federaland Akins classifiers, and is by way of example illustrated on the accompanying drawing as applied to a Federal drag classifier.

0n said drawing:

Fig. 1 is a diagrammatic side elevation of a Federal drag classifier.

Fig. 2 is a plan view of the separating tank with associated means for supplying additional washing water.

Fig.3 is a detailed view, partly in section showing the sieve member and the mode of attaching it to the belt.

Fig. 4 is an end view of the member as shown in Fig. 3.

Fig. 5 isa view similar to that of Fig. 3'

showing in. addition a preferred embodiment of the topmost portion of the tank with the means. for supplying washing water, and additional passages the object of which will clearly appear from the following. n

Fig. 6 shows a side elev'ationof the topmost portion of the tank with said additional passages, the means for supplying washing water being omitted for the sake of clearness.

Corresponding parts are represented by similar reference numerals throughout the drawing. j r

1 denotes a frame carrying the separating tank 2 comprising side walls interconnected by an inclined bottom 3 and a curved ascending lower end portion 4. Mounted on the framev 1 are bearings 5 and 6 receiving shaft 7 and 8, respectively, carrying lower and upper drums'9 and 10, respectively, for guiding an endless belt 11 carrying rakes 12. 14 represents a feed box and 13 is a launder to receive the coarse material. An overflow for the fine material is indicated at 15 in Fig. 1.

The drums 9 and 10 are rotated in the conventional way and the rakes when moving with the belt 11 carry the coarse material which settles to the bottom of the tank up the sloping surface 3 and discharge it into the launder 13. Due to the fact that the rakes 12, according to the invention, are con structed as sieves, as may be seen from Fig. 3,

adapted to retain the coarse material and pass through the fine material, any fine material which may have settled with the coarse material is prevented from being removed therewith by passing back through the sieves to the liquid pulp in the settling portion of the tank 2, to be discharged with the bulk of the fine material through the overflow 15.

To assist in this action additional washing water may be supplied to the material on the sieves after the latter have left the pulp. To this end water is supplied by a pipe 16 to distributing boxes 17 which through perforations in the adjacent portions of the bottom of the tank 2 supply water to the material on the sieves after the latter have left the liquid pulp thereby effecting a washing-01f of any fine material're'maining on the sieves for the purpose of facilitating its return to the liquid pulp. In certain cases I have found it preferable to arrange one or a plurality of such distributionboxes also below the level of the pulp in that region thereof which the sieves pass through shortly before they ascend from the ulp whereby the ascending motion of the ne material is amplified. If desired the washing as effected by the water delivered from boxes 17 may be assisted by lateral nozzles 18 which eject more or less transverse currents of water onto the material on the sieves. Said nozzles 18 are supplied with water by means of pi es 19 which as well as pipe 16 may be fed mm a common source of water under suitable pressure connected to pipe 31.

Figs. 3 and 4 show a preferred embodiment of the sieve members and their support. As

here shown sieves 20 are clamped between plates 21 and the lower portion of angle bars 22 arranged at opposite edges of the belt 11 and riveted thereto as indicated at 23 in Fig. 4, said plates and angl bars being interconnected by screws &0. As shown in Fig. 3 a space 24 is left between the top edge of the sieves 20 and the belt 11 to permit some of the washing water to overflow, passing through the space 24 with parts of the fine material and flow back to the liquid pulp in the settling portion of the tank 2. Instead of having water and fine material overflow in this way it may in certain cases especially when treating materials having a pronounced tendency to shut up the sieves be suitable to arrange for a lateral overflow into passage 25 asshown in Figs. 5 and 6 thereby preventing the washed-oil fine material from being supplied to the sieves behind the sieve from which the fine material has been washed off. Said passages 25 extend along the upper sloping edges of the topmost portions 26 of the walls 30 which edges in thiscase are situated somewhat below the upper edges of the sieves as may be clearly seen from Figs. 5 and 6. Said passages 25 carry the washing water with its contents of fine material washed-oil back to the liquid pulp at or near the level thereof through openings 27 in the portion 26.

What I claim is:

A mechanical classifier comprising a tank to receive a pulp of water and coarse and fine materials to be separated, movable sieve members to discharge the coarse material settling to the bottom of said tank and constructed to pass through the fine material, means to supply additional water to the material on said sieves during their passage from the pulp to a discharge for the coarse material so as to wash ofi any fine material remaining on said sieves and a lateral assage or passages outside said tank to a low those portions of said last mentioned material which do not pass back through said sieves to return through said passage or passages to the pulp in the .tank.

In testimony whereof I affix my signature.

. ERNST JOHAN AXEL ROTHELIUS. 

